A 21 year old man with clinical features of acromegaly, elevated IGF-I, undetectable plasma GH, and no pituitary enlargement on MRI was recently seen at OHSU. Other family members have similar features. We will evaluate the propositus with a detailed 24-hour examination of plasma GH, TSH, and PRL, and cortisol. If warranted by the data thus obtained, other family members will be evaluated to ascertain the existence and penetrance of this previously undescribed condition.